Cryptology ePrint Archive: Report 2009/555

Abstract: Password-based Authenticated Key Agreement (PAKA) protocols are widely used in wireless mobile networks, however many existing PAKA protocols have security flaws. In the 3GPP2 network, there are several PAKA protocols proposed to enhance the security of the Authentication Key distribution mechanism which is subjected to the Man-In-The-Middle attack. We point out the security flaws of such protocols in [4,5] and give two practical attacks on them. Moreover we propose an enhanced PAKA protocol that can resist undetectable on-line and off-line password guessing attacks, and formally analyze its security in the Random Oracle model. In addition, we consider a special version of Diffie-Hellman problem called Degenerate Diffie-Hellman problem and propose two assumptions called Computational and Decision Degenerate Diffie-Hellman assumption which are as difficult as CDH assumption and DDH assumption respectively.